The present invention relates to a disposable hypodermic syringe for use in injecting or withdrawing fluids that is adapted to prevent accidental needle sticks and to be rendered nonreusable subsequent to initial use.
In the health care field, medical practitioners such as nurses and doctors, as well as related personnel such as clean-up workers and the like, are subject to the hazard known as "needle stick". A needle stick occurs when the epidermis of a person who is not the intended subject of an injection or fluid withdrawal is punctured by a hypodermic needle, especially after the needle has been used on another person who could be contaminated with a transferable microorganism. Needle sticks may occur when health care workers attempt to recap syringes after use. This is usually due to the worker being careless in trying to guide the needle into the relatively small opening in the cap or when the worker is bumped during the capping process. Sticks also occur when a cap is dislodged from the needle during handling or when uncapped needles are encountered by cleaning persons. Used needles pose a potential threat of transfering dangerous microorganisms until fully destroyed due to such sticks.
While it is possible for a health care worker to be stuck prior to use of the needle in a patient and then have the needle pass on infectious material from the worker to the patient, needle sticks are usually most hazardous when occurring subsequent to use of the needle for injection or withdrawal of fluid from a patient carrying a communicable virus such as the hepatitis or AIDS (auto immune deficiency syndrome) causing viruses. Before the widespread incidence of AIDS, a stick was usually followed by a shot of a passive immunizing agent (immune serum globulin) to reduce the chance of contacting hepatitis. Because there is no known immuglobin or anti-serum to treat the AIDS causing viruses, preventing needle sticks with hypodermic needles contaminated with the AIDS viruses is of paramount concern. The need to prevent needle stick is heightened due to the current inability of medical practitioners or hospitals to force patients to be tested for AIDS prior to treatment or, even if tests are conducted, to be able to detect AIDS or exposure to the AIDS causing viruses during the first several months after exposure. It is foreseeable that a person receiving a needle stick may engage in conduct which would unknowingly again transmit the virus. Even where communicable diseases are not a threat, subjects of needle sticks are generally required to receive injections of immune serum globin as a precautionary measure resulting in discomfort and apprehension by the recipient as well as additional testing and cost to the responsible health care facility.
In addition to the threat of needle stick, it is known that in underdeveloped countries hypodermic syringes are often reused without proper sterilization. Also, used syringes are known to fall into the hands of illegal drug users who may pass the syringe between users and use the syringes multiple times without sterilization to inject themselves and others. The availability of operable used syringes arguably is thus a contributing cause of continued drug abuse and one key factor in the transmission of diseases by users of illegally administered drugs.
Numerous modified syringe configurations and appliances have been developed in recent years to lessen the likelihood of needle stick occurrences. Additionally, several alternative disposable syringes have been developed which may be rendered inoperable after use to combat drug abuse and the transfer of disease.
In particular, devices have been manufactured or suggested that are directed toward reducing the needle stick hazard and may be, in general, divided into two categories. First, are those devices that assist the user in resheathing or recapping the needle after use. The resheathing devices generally either provide a mechanism for replacing a detachable cap or sheath without the need for the user's hands coming into proximity to the needle point or contain a movable cylinder located concentrically about the syringe cylinder which may be slidably moved axially along the syringe and relocated around the needle thereby covering and protecting the point.
The second category of devices developed for the avoidance of needle stick occurrences incorporate various mechanisms for retracting the needle into the hollow cylinder body after use.
The principle short-coming of the devices that assist the user in recapping or resheathing the needle is that the syringe is not rendered inoperable after use. Secondly, the caps are prone to be lost or fall off after recapping thereby becoming a later hazard to those subsequently handling the used syringe. Designs in this category include: U.S. Pats. to Pedicano, Pat. No. 4,610,667; Vennon, Pat. No. 4,596,562; and Sampson, Pat. Nos. 4,573,976 and 4,425,120.
The retracting needle devices likewise have significant short-comings. First, several of the designs, notably, U.S. Pats. to Haber, Pat. No. 4,710,170 and Jagger, Pat. No. 4,592,744, must be partially disassembled to be rendered safe. Disassembly is time consuming and potentially confusing for users. Additionally, the disassembled components may themselves be contaminated, defeating the objective of disassembly. An alternative category of retracting needle designs (as shown in U.S. Pat. to DeLuccia in FIGS. 5 and 6, Pat. No. 4,675,005) incorporates a threaded post on the fluid engaging face of the syringe piston to attach to a needle support or base structure and is supposedly designed to allow the needle base structure to detach from the syringe cylinder head by screwing the base structure into the cylinder head then reverse unscrewing the post from the base structure, thereby permitting the needle to be retracted along with the piston into the hollow cavity of the syringe cylinder. Unfortunately, for this later device, there is no effective means of determining whether the post will unscrew from the base structure or the base structure will unscrew from the cylinder, hence, this structure was apparently not found as satisfactory as one using a snap-in ring described in the same reference to hold the base structure in place while the post was withdrawn.
One of the primary short-comings of the existing retracting needle designs is that each requires use of a non-standard needle support structure. That is, a needle with a base that has to be specially manufactured as opposed to using standard parts. Non-standard components create problems of familiarity among users with the new syringe and lack of interchangeability with available needle configurations in addition to substantial added cost. Lack of familiarity increases the likelihood of accidents resulting from misuse and decreases likelihood of acceptance by users.
Lack of interchangeability precludes use of existing luer lock cannulas with the new syringes. For example, in the DeLuccia reference, the three embodiments shown each require a differently configured cannula or needle base, none of which include standard luer lock fittings.
Additionally, none of the retracting needle designs provide the dual capability of being used as a conventional syringe with a front mounting luer lock fitting available, should a user have a special requirement and conventional mounting is desired.
Not only is it desirable for a user to be able to both retract the needle of the syringe and thereafter make the syringe unreusable, but also, it is desirable that the same syringe be able to provide other features that make the concept suitable for a wide number of uses and under a variety of conditions. For example, it is desirable to make a device of this type that is usable not only as a syringe for delivering fluids or withdrawing fluids from a patient, but also usable in conjunction with a vacutainer, arterial catheter assembly, a spinal tap apparatus or any similar device having a hypodermic needle, in order to protect the health care provider while allowing access to fluid therein if so desired.
In addition, it is desirable for a syringe of this type that, when a plunger of the syringe is completely depressed, there is very little or virtually no air remaining in the interior of the syringe. This helps in assuring that air is not accidentally entrained with liquid being injected into a patient.